Anti-reflective structures have been found in nature and utilized in various man-made apparatuses. It was discovered that the eyes of night-flying moths have excellent anti-reflective properties. The moth-eye structure is based on the principle of a gradient index of refraction. The tiny features on a moth-eye surface have a continuous refractive index gradient, thereby reducing the light reflection on the moth eye surface. Anti-reflective coatings have been used in various applications, such as the anti-glare coating used on corrective lenses and camera lens.